Spray application is the preferred mode of product delivery in a gamut of industries including coatings and paint, personal care, HI&I, food and beverage, transportation, agriculture, and many others. Accurate measurement of crucial spray characteristics like drop size distribution, coverage, atomization, droplet velocity, drop rebound, and spray drift are important to ensure spray systems meet the delivery and efficacy demands of the application. Sophisticated transmittance-based non-intrusive methods such as laser diffraction (PMS, e.g., Malvern, Sympatec), laser interferometry (PDA, PDPA), pulsed laser backlit-high speed image analysis (PDIA e.g., Oxford VisiSizer, LaVision ParticleMaster), and high-speed videography are most commonly used for spray characterization. Though highly efficient and extremely accurate, the instrumentation can be expensive, complicated to operate, sensitive to drop shape, limited by optical density of spray media, and sensitive to external elements like vibration and temperature, coupled with a very narrow field of view which can restrict wide scale adoption and field deployment of these methods.
The industry requirement of dispensing materials to targets across a myriad of conditions of surface topology, applications, material injection and processes has undoubtedly made spray delivery systems the most universal, versatile, economic and efficient mode of controlled material delivery. In agriculture, the overall quality of pesticide and agricultural sprays generated by varied types of agricultural hydraulic nozzles play a crucial role in determining crop or leaf coverage, active deposition, and most importantly environmental and public health impacts from material translocation and loss arising from off target spray drift, all of which ultimately culminate into the efficacy and sustainability of the spray application processes. Unlike industrial spray applications, accurate real-time evaluation of agricultural sprays in action is further complicated by plant (crop or weed) architecture and dynamics of local meteorological conditions (wind speed, wind direction, humidity and temperature) with the closest approximation to in-field spray performance of nozzles and materials being achieved by wind-tunnel methods under precisely controlled laboratory conditions using strictly laboratory-based spray characterization and analysis equipment.
With the constant rise in concern over off-target spray drift in agricultural applications and significant activity around mitigating the drift problem, closely and accurately monitoring spray characteristics is desirable. Determining nozzle and material influences on spray drift potentials, such as droplet size distribution, droplet velocity distribution and trajectories, volume distribution patterns, spray sheet structures and lengths, entrained air characteristics and structure of individual spray droplets has gained in importance.